1. Field of the Invention
This invention relates to the determination of network interface transmission modes and the calculation of bandwidth utilization in a network interface.
2. Description of the Related Art
In a digital network, each device connected to a network does so through an interface. The interface acts as communication gateway from one device to another. Computer network communication may comply with a particular network protocol such that inter-device communication can take place. When a network grows larger, it becomes necessary to manage each device (node) within the network and the overall network. One such standard for managing a network is the Simple Network Management Protocol (SNMP). Under the SNMP architecture, small management programs known as agents, run in, each managed node such as, for example, network interface cards, servers and routers. Agents monitor their devices and gather statistical information in a format known as Management Information Base (MIB). A central management console program typically calls the agent on a regular basis and downloads the contents of the managed device's MIB.
As a computer network may be built over time, the computer within the network or the interfaces on each computer may vary. One aspect of the interface that can vary is the transmission modes that an interface can support. The communication mode an interface can support can be a full-duplex or half-duplex. In full-duplex, an interface can transmit and receive information at the same time. In half-duplex, an interface can receive or transmit data one at a time but not simultaneously. The interface may also be operating in a simplex mode, where the interface can communicate data only in one direction, either sending or receiving. The operational mode an interface can support may be coded into the MIB on the interface as described in IETF RFC 2233, published in November 1997. Since it is not mandatory to keep or store an interface's operational mode in its associated MIB, most hardware interfaces do not keep such information in MIB. Therefore, the information in MIB alone is not a reliable indication whether a hardware interface can support either the half-duplex or the more advanced full-duplex mode.
In many modern network interfaces, the full-duplex mode is supported in hardware. Because of the mixture of equipment in any particular network system, to make the computer network system operable, many network managers set the default mode for any interfaces to auto-detect and use full-duplex mode if possible and half-duplex mode if not. When an interface is operating in a half-duplex mode the available bandwidth is much less than when the interface is operating in the full-duplex mode, as little as 20 to 30 percent of the full-duplex mode.
In a managed network, bandwidth utilization is a key metric to the health or operational state of the network. The bandwidth utilization of an interface indicates whether the network interface or that portion of the network is light in network traffic, fully loaded or in need of additional capacity. It will be recognized that bandwidth utilization may be calculated from the traffic data through the interface and depends on which mode the interface is operating in. When the bandwidth utilization at a particular interface reaches a certain level, the agent or the management console will typically raise an alarm. This may cause the network manager to reroute network traffic flow to force a reduction in bandwidth utilization so as to avoid network traffic breakdown. This will reduce the network's effective bandwidth utilization. Typically, changing interfaces or increasing their capacity in a business enterprise network system is complex and costly. Thus, it would be very beneficial to accurately calculate the bandwidth utilization and plan the network interface capacity accordingly.
Therefore, it is desirable to have a reliable technique to determine the actual capability of a particular interface in a digital network system, such as a business enterprise network system. It is also desirable not to disturb the network system or create a large amount of network management overhead in determining the actual interface capability.